A radiobiological study of the schemes with a low number of fractions in high-dose-rate brachytherapy as monotherapy for prostate cancer
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AuthorGuirado Llorente, Damián; Ruiz-Arrebola, Samuel; Tornero-López, Ana M.; de la Vega, Jose M.; Prada, Pedro J.; Lallena Rojo, Antonio Miguel
HDR brachytherapyProstate cancerMonotherapy
Damián Guirado, Samuel Ruiz-Arrebola, Ana M. Tornero-López, et al. A radiobiological study of the schemes with a low number of fractions in high-dose-rate brachytherapy as monotherapy for prostate cancer. J Contemp Brachytherapy. 2020;12(2):193‐200. [doi:10.5114/jcb.2020.94492]
SponsorshipSpanish Ministerio de Ciencia y Competitividad FPA2015-67694-P; European Union (EU); Junta de Andalucía FQM0387
Purpose Schemes with high doses per fraction and small number of fractions are commonly used in high-dose-rate brachytherapy (HDR-BT) for prostate cancer. Our aim was to analyze the differences between published clinical results and the predictions of radiobiological models for absorbed dose required in a single fraction monotherapy HDR-BT. Material and methods Published HDR-BT clinical results for low- and intermediate-risk patients with prostate cancer were revised. For 13 clinical studies with 16 fractionation schedules between 1 and 9 fractions, a dose-response relation in terms of the biochemical control probability (BC) was established using Monte Carlo-based statistical methods. Results We obtained a value of α/β = 22.8 Gy (15.1-60.2 Gy) (95% CI) much larger than the values in the range 1.5-3.0 Gy that are usually considered to compare the results of different fractionation schemes in prostate cancer radiotherapy using doses per fraction below 6 Gy. The doses in a single fraction producing BC = 90% and 95% were 22.3 Gy (21.5-24.2 Gy) and 24.3 Gy (23.0-27.9 Gy), respectively. Conclusions The α/β obtained in our analysis of 22.8 Gy for a range of dose per fraction between 6 and 20.5 Gy was much greater than the one currently estimated for prostate cancer using low doses per fraction. This high value of α/β explains reasonably well the data available in the region of high doses per fraction considered.